1. Field of the Invention
The present invention relates to control mechanisms, and more particularly to control mechanisms for hydraulic valves.
2. General Background
Hydraulic speed control valves are used in heavy machinery such as cranes, bulldozers, and dredges to control hydraulic flow in the heavy machinery. Hydraulic speed control valves are located between a hydraulic pump and a four-way, three position control valve. The hydraulic flow drives a unit in the heavy machinery which is being operated. The four-way, three position valve determines whether the unit will be driven forward, in reverse, or not driven at all. Hydraulic speed control valves are presently controlled by Morse control cables. A Morse control cable comprises an inner cable which is disposed within a co-axial cylindrical housing and which may be pushed and pulled. The inner cables often rust to the point where they are rendered inoperative. Also, Morse control cables are not good for long distances, since it is difficult to push the inner cable very far. Maintenance of these cables is a source of inconvenience and expense for heavy machinery operators.
Various controls have been proposed for valves.
Comeau (U.S. Pat. No. 2,662,547) discloses flow control apparatus for automatically controlling flow of air to the cabin.
Jordan (U.S. Pat. No. 3,258,985) discloses an electric control apparatus for a valve activator which moves the valve between two preselected positions.
Gupta (U.S. Pat. No. 4,455,012) discloses an electric control capable of moving a valve between two positions.
An (U.S. Pat. No. 4,538,789) discloses an actuator for moving a valve between an open and a closed position.
Rollins (U.S. Pat. No. 4,556,832) discloses electrical apparatus for moving a valve between three positions.
Hewitt (U.S. Pat. No. 4,611,617) discloses an electrical apparatus for moving a valve between an open and a closed position.
Fukamachi (U.S. Pat. No. 4,621,789) discloses an electrical apparatus for moving a valve between an open and a closed position.
DePirro (U.S. Pat. No. 4,624,280) discloses a system for automatically opening and closing a gate valve in response to the rising or falling of fluid level in a pipe.
None of these patents discloses apparatus for electrically controlling a hydraulic speed control valve from a position remote from the speed control valve.